In recent years, there has been achieved a multi-antenna transmission system in which a transmitter and a receiver use multiple antennas to transmit and receive radio signals in order to improve utilization efficiency of radio frequencies. In general, Multi-Input Multi-Output (MIMO) technique is introduced in the multi-antenna transmission system.
In such a multi-antenna transmission system, channel information (hereinafter, abbreviated as MIMO CSI as needed) indicating a transmission path characteristic on a receiver side in a MIMO environment can be estimated on a transmitter side using the reversibility of a propagation path in time division duplexing, or by using a feedback channel also in frequency division duplexing (FDD). Accordingly, there has been known a method of predicting MIMO CSI in the future, i.e., at the time of transmitting the next radio signal by using the past and current MIMO CSI (see, non-patent literature 1 and non-patent literature 2).
Specifically, proposed is a method of multiplying MIMO CSI by a simple beamspace transformation matrix. In this method, a linear prediction (AR-LP) based on an autoregressive (AR) model is implemented for each element of a transformation MIMO CSI obtained by multiplying the MIMO CSI by a beamspace transformation matrix. Furthermore, the prediction value of MIMO CSI at the time of transmitting the next radio signal can be obtained through inverse transformation of the prediction value of the transformation MIMO CSI obtained by performing the linear prediction.    Non-patent literature 1: T. Eyceoz, S. Hu, and A. Duel-Hallen, “Performance Analysis of Long Range Prediction for Fast Fading Channels,” Proc. of 33rd Annual Conf. on Inform. Sciences and Systems CISS'99, Vol. II, pp. 656-661, March 1999.    Non-patent literature 2: T. Svantesson, A. L. Swindlehurst, “A Performance Bound for Prediction of MIMO Channels”, IEEE Trans. Signal Process., vol. 54, no. 2, pp. 520-529, Feb. 2006.